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In situ study on kinetics of phase transformations and thermal stability of retained austenite in TRIP-assisted advanced high strength steel

Grant number: 14/20844-1
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): September 01, 2014
Effective date (End): February 01, 2018
Field of knowledge:Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
Principal researcher:Paulo Roberto Mei
Grantee:Julian David Escobar Atehortua
Home Institution: Faculdade de Engenharia Mecânica (FEM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
Associated scholarship(s):16/13466-6 - Correlative atom probe tomography and transmission electron microscopy on the study of M/A, B/A interfaces and precipitates after in situ heat treatments for a TRIP-assisted supermartensitic stainless steel and advanced high strength steel, BE.EP.DR


Advanced high strength steels with transformation induced plasticity effect (TRIP-assisted AHSS), have been widely used in the automotive industry due to their excellent balance of high mechanical strength, good formability and low cost. To provide them with TRIP effect, it is necessary to perform isothermal heat treatments to stabilize austenite in room temperature, typically known as retained austenite (Ar). After that, and taking advantage of the high strain hardening rate provided by the TRIP effect, these alloys are subjected to cold forming processes to produce auto body components. The superior formability of TRIP-assisted AHSS is controlled by the Ar fraction and its mechanical stability, which provide high work hardening rate. On the other hand, the Ar thermal stability is also important due to its possible decomposition during the paint baking and galvanizing processes, compromising the material performance. The objective of this research is to perform time-resolved studies of the kinetics of austenitic formation and decomposition during the heat treatment and reheating stages involved in the processing of TRIP-assisted AAAR. This will be achieved by real time X-ray diffraction measurements during thermo-mechanical processing of the material at the XTMS experimental station at the Brazilian synchrotron light source. Further material characterization including scanning and transmission electron microscopy, and atom probe tomography will support the study of fundamental aspects of diffusive and martensitic phase transformations. In addition, the intended scientific results will make possible further optimization of industrial processing conditions for these materials.

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Scientific publications (5)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
CONDE, F. F.; ESCOBAR, J. D.; OLIVEIRA, J. P.; JARDINI, A. L.; BOSE FILHO, W. W.; AVILA, J. A.. Austenite reversion kinetics and stability during tempering of an additively manufactured maraging 300 steel. ADDITIVE MANUFACTURING, v. 29, . (14/20844-1, 19/00691-0, 17/17697-5)
ESCOBAR, J. D.; FARIA, G. A.; MAIA, E. L.; OLIVEIRA, J. P.; BOLL, T.; SEILS, S.; MEI, P. R.; RAMIREZ, A. J.. Fundamentals of isothermal austenite reversion in a Ti-stabilized 12Cr-6 Ni-2 Mo super martensitic stainless steel: Thermodynamics versus experimental assessments. ACTA MATERIALIA, v. 174, p. 246-259, . (16/13466-6, 14/20844-1)
ESCOBAR, J. D.; OLIVEIRA, J. P.; SALVADOR, C. A. F.; FARIA, G. A.; POPLAWSKY, J. D.; RODRIGUEZ, J.; MEI, P. R.; BABU, S. S.; RAMIREZ, A. J.. Meta-equilibrium transition microstructure for maximum austenite stability and minimum hardness in a Ti-stabilized supermartensitic stainless steel. MATERIALS & DESIGN, v. 156, p. 609-621, . (16/13466-6, 14/20844-1)
ESCOBAR, J. D.; FARIA, G. A.; WU, L.; OLIVEIRA, J. P.; MEI, P. R.; RAMIREZ, A. J.. Austenite reversion kinetics and stability during tempering of a Ti stabilized supermartensitic stainless steel: Correlative in situ synchrotron x-ray diffraction and dilatometry. ACTA MATERIALIA, v. 138, p. 92-99, . (16/13466-6, 14/20844-1)
ESCOBAR, J. D.; POPLAWSKY, J. D.; FARIA, G. A.; RODRIGUEZ, J.; OLIVEIRA, J. P.; SALVADOR, C. A. F.; MEI, P. R.; BABU, S. S.; RAMIREZ, A. J.. Compositional analysis on the reverted austenite and tempered martensite in a Ti-stabilized supermartensitic stainless steel: Segregation, partitioning and carbide precipitation. MATERIALS & DESIGN, v. 140, p. 95-105, . (16/13466-6, 14/20844-1)
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
ATEHORTUA, Julian David Escobar. Austenite reversion kinetics and thermal stability during the inter-critical tempering of a 12Cr-6Ni-2Mo-0.02C-0.13Ti. 2018. Doctoral Thesis - Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica Campinas, SP.

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